pinctrl: intel: fix build warnings about export.h

After commit a934a57a ("scripts/misc-check: check missing #include
<linux/export.h> when W=1") and 7d95680d ("scripts/misc-check:
check unnecessary #include <linux/export.h> when W=1"), we get some build
warnings with W=1:

pinctrl-intel.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing

So fix these build warnings for the driver code.

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>